Evaporation from reservior too low

[dave brauer]

Dear fellow users,

I am modeling a river basin in the Southern High Plains (USA) where evaporation rates can be quite high (open pan Evaporation = 100 inches or 2500 mm annually).

The local lake managers are esitmating evaporation from their reserviors at similar rates as above.

I currently have the reservior evaporation set at max (1) and the model is pulling weather data from what are appropriate stations.

However the model is reporting evaporation ates that are about 1/10th that of the lake managers are estimating.

Any thoughts?

Dave

[Jim Almendinger]

Dave --
What output are you looking at?  If you're looking at the rate given near the bottom of the output.std file, I believe the mm of evaporation reported for reservoirs is a watershed-wide number as a component of the annual water budget.  I.e., the total volume of water evaporated from reservoirs (annually), divided by the total watershed area (not just the reservoir area), and expresses as mm.  So if your reservoir is about a tenth of the area of the watershed, then the actual rate over the reservoir would be about 10x larger. 
Here's hoping it's that simple...
-- Jim

---

From: "dave brauer" <super_e...@yahoo.com>
To: arc...@googlegroups.com, swat...@googlegroups.com
Sent: Tuesday, September 13, 2011 11:14:24 AM
Subject: [SWAT-user:2986] Evaporation from reservior too low

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--
Dr. James E. Almendinger
St. Croix Watershed Research Station
Science Museum of Minnesota
16910 152nd St N
Marine on St. Croix, MN  55047
tel: 651-433-5953 ext 19

[dave brauer]

Thanks for the reply Jim,   I am looking at both the output text file (summary) the res file in the mbd output file. They seemed to be giving the same number. For the output text file, I took the ave evaporation for the watershed and tiimes against the area of the reservior to get evaporation.   However the simulation I was looking at the surface area of the reservior was quite low for I was trying to better understand the consumptive use and min out flow varibales in the monthly input edits.   I need to check the numbers again... I may be wrong that I am that far off.   Dave --- On Tue, 9/13/11, Jim Almendinger <din...@smm.org> wrote:

[dave brauer]

I am admitting to being stupid and apologizing for starting this thread. Thanks to all that replied.   It turns out that I was comparing monthly values of evaporation in my run to annual totals in the reports from the lake operators. No wonder it was off by about 10x !   again my apologies for wasting anyone's time !   Dave --- On Tue, 9/13/11, dave brauer <super_e...@yahoo.com> wrote: